From Google Developer Support:
Regarding ARC on 32-bit Chromebooks...
We do not support the 32-bit x86 chromebooks because the performance is too poor, and the graphics compatibility is not complete either (though I forget the details now).
There are only 3 of these devices, launched in 2010 and 2011, and they are now past the official 5-year EOL support date, though I think they're still getting updates currently:
1) the original Cr-48, this was the pilot device which was distributed to enthusiasts and not sold IIRC
2) Acer AC700
3) Samsung Chromebook Series 5 (not the series 5 550, released a year later)
I believe we are properly excluding these platforms from downloading ARC apps from the webstore, but maybe not, and if you're doing enterprise deployments it may bypass this. I really think it's unlikely these devices have a significant user base, especially in EDU today.